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VW Polo 1.4 BUD 2008 - Misfire to #3 cylinder, code P0203 - Fixed #

Posted by Paul Goswell on May 29, 2013, 3:44 pm

Year of Manufacture *: 08
Engine Size and Code *: 1.4 16v BUD
( Optional ) ECU Type: magneti marrelli
( Optional) Fault Codes: p0203

misfire no 3 cylinder, no pulsed earth to injector, ive traced wire back to ecu which is clipped to n/s bulk head broken wire so sounds like the ecu is faulty any body had this problem

Re: vw polo

Posted by Kevin Apps <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT2589' width='330' height='300' border=0 style='border:none;'> on May 29, 2013, 5:33 pm, in reply to "vw polo"
Kevin Apps

Paul.

"no pulsed earth to injector"

ECU shutting down the injector to save the CAT ?

Kev.

Re: vw polo

Posted by paul goswell <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT5240' width='330' height='300' border=0 style='border:none;'> on May 29, 2013, 5:55 pm, in reply to "Re: vw polo"
Paul Goswell

this vehicle did come in 6months ago with a miss fire on the same cylinder, which was the coil and was replaced with genuine coil and went out ok no problems, i have rechecked the coil with another one and changed the plug but still misfiring its not a compression problem as its the earthing side of injector any other ideas

Re: vw polo

Posted by aidan birley <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT2879' width='330' height='300' border=0 style='border:none;'> on May 29, 2013, 8:33 pm, in reply to "Re: vw polo"
Aidan Birley

Paul

Have you taken on board kev's suggestion ?

How are you testing the pulsed earth ?

Aidan

Re: vw polo

Posted by Paul Goswell on May 29, 2013, 9:01 pm, in reply to "Re: vw polo"
Edited by board administrator May 31, 2013, 12:40 pm

i have disconnected injector while its running fitted a little noid light and its not flashing checked no2 cylinder and it i,s i then checked live feed to one side of connector which was ok so it must be losing its switched earth side i then traced wire back to ecu to check continuity which was ok.

Re: vw polo

Posted by colin Hedger <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1335' width='330' height='300' border=0 style='border:none;'> on May 29, 2013, 9:30 pm, in reply to "Re: vw polo"
Colin Hedger

Be very careful Paul.
I would look again at the injector shutting down as per kevins suggestions.
I had one of these with the self same set of symptoms, although it was on a BBY engine.
mine was slightly down on compression on that cylinder and it took me ages to work out what was going on.
In my case only a major engine strip would have sorted it (pistons/rings).I think most of these small 16v VW engines are prone to ring problems.I also think the engine management is far too sensitive on these engines.
Mine had only done 40k.
HTH

Colin

Re: vw polo

Paul

Have you taken on board kev's suggestion ? ?

wiring needs to be load tested,(if not already done,) not just continuity.

Injector wiring would be better tested (monitored) with a scope, including activity on start up.

Cheers Aidan

Re: vw polo

Posted by Paul Goswell on May 29, 2013, 10:01 pm, in reply to "Re: vw polo"
Edited by board administrator May 31, 2013, 12:41 pm

ok will check compressions in the morning and scope injector wiring thanks paul

Re: vw polo

Posted by Lee Mackintosh <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1348' width='330' height='300' border=0 style='border:none;'> on May 29, 2013, 10:41 pm, in reply to "Re: vw polo"
Lee Mackintosh

I would probably also consider swapping injector to another cylinder if its easy enough to do.

If misfire code follows suit then its most likely an injector.

I had this issue with a 12 valve skoda recently after having all the valves and seats replaced due to a severe lack of compression. Would run fine then suddenly drop into limp mode.

Re: vw polo

Posted by paul goswell <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT5240' width='330' height='300' border=0 style='border:none;'> on May 30, 2013, 7:21 am, in reply to "Re: vw polo"
Paul Goswell

thanks lee but if the noid light is not flashing its got to be a supply voltage or earth on that loom or connector

Re: vw polo

Posted by lee mackintosh <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1348' width='330' height='300' border=0 style='border:none;'> on May 30, 2013, 8:19 am, in reply to "Re: vw polo"
Lee Mackintosh

So if you clear codes then restart vehicle is it instantly misfiring.

If not, then if you use the noid light on the next startup does the noid light flash as it should.

Doesn't take long for the misfire count to build up then the ecu will shut down the cylinder specific injector.

If compression is equal and good (i had a polo in with just over a bar difference that misfired due to valve issues) then i'd suspect an injector if ignition coils have been swapped about.

thanks
lee

Re: vw polo

Posted by Jim Power <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=ukat3202' width='330' height='300' border=0 style='border:none;'> on May 30, 2013, 8:55 am, in reply to "Re: vw polo"
James Power

The scope will tell you a lot. You may see some firing events before it shuts down. Easy to miss with the naked eye or ear.
Jim.

jim power

Re: vw polo

Posted by paul goswell <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT5240' width='330' height='300' border=0 style='border:none;'> on May 30, 2013, 10:02 am, in reply to "Re: vw polo"
Paul Goswell

checked compressions when cold all good, gave a run round block and misfire seemed to come and go, rechecked compressions no3 slightly down on the rest so kev was right ecu shutting down, i rechecked no 3 injector feed and live ok and earth switching so looks like could be head off dont know whether to forte flush and gas treatment as the car is a auto and only done 50,000 miles driven by an old lady could be sticky valves or rings ?

Re: vw polo

Posted by Pete Mutlow <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1569' width='330' height='300' border=0 style='border:none;'> on May 30, 2013, 6:16 pm, in reply to "Re: vw polo"
Peter Mutlow

Hi Paul,

For my tuppence worth I would let the customer make an informed decision. The Forte treatment could well work and save the lady a lot of money. However she should be advised that it is not a 100% guaranteed cure. I reckon its worth a shot unless you need the work to remove the head etc.

Regards

Pete M

Re: vw polo

Posted by James Eardley <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=ukat3143' width='330' height='300' border=0 style='border:none;'> on May 30, 2013, 7:29 pm, in reply to "Re: vw polo"

Hi Paul

Can you monitor the misfire counts... most scan tools will show this Im sure... VCDS is fantastic and cheap if you haven't got it already.

Watch the misfire counts and see under what conditions generates the most misfires, then do the relevant tests under these conditions.

Lee mentioned the one he had with only a 1bar pressure difference.... I too have had this a few times.

A cylinder leak down test may help.

Also use the misfire counter if you swap any parts round ie, injectors, coils ect...

WPS is the Daddy for smoking compression faults on these engines.

hth
James

Re: vw polo

Posted by paul goswell <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT5240' width='330' height='300' border=0 style='border:none;'> on May 30, 2013, 8:45 pm, in reply to "Re: vw polo"
Paul Goswell

well the forte did not work so the car is coming back in next week to remove the head for inspection excuse my ignorance james but what is wps thanks paul

Re: vw polo

Posted by Lee Mackintosh <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1348' width='330' height='300' border=0 style='border:none;'> on May 30, 2013, 9:06 pm, in reply to "Re: vw polo"
Lee Mackintosh

Can you also do a relative compression test just to see if its noticeable on the scope image.

WPS is a vacuum/pressure transducer that members like james use for doing in cylinder running compression tests to great effect.

They can confirm many issues such as valve timing inaccuracies, valve leaking etc without to much dis-assembly of timing covers etc.

Just look through the scope forum section as I'm sure there is an example of it in use.

Well beyond me some of the diagnostics they do with it.

Re: vw polo

'excuse my ignorance james but what is wps thanks paul'

Not at all mate.

I think Lee explained the WPS excellent

It is one of them tools you have to practice with or you will find it hard to use and time consuming and it will end up in a cupboard gathering dust.... I know, I have done this twice LOL

It is worth practicing though... it is a very good friend when you suspect compression issues

This management systems monitors even slight misfires very closely and is keen to save the CAT hence shutting off the injector.
It is amazing the small differences in cylinder pressure that can cause the above chain of events...

With this engine... even the WPS can't save you sometimes... but a standard compression gauge will point the fault out like a sore thumb.

When approaching one of theses bast$%ds with a misfire LOL

Watch the misfire counts like a hawk, just like the ECU does. You should be able to see what makes the misfire counter tick and find the ideal condition to do your tests... keep an open mind and suspect ign, fuel and compression because these have them all!

If it turns out to be compression then I like to know the cause before the head comes off because the fault is not always obvious and then you have to worry until the car is put back together.

Bang the cylinder leak down tester in the offending cylinder.

What are your compression results hot and cold?

What conditions makes the misfires more frequent... try this with different loads whilst stationary aswell, if you can re-enact the misfire in the garage it makes life easier when doing the testing

hth
James

Re: vw polo

Posted by Jon Morgan <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=ukat3190' width='330' height='300' border=0 style='border:none;'> on May 31, 2013, 2:00 pm, in reply to "Re: vw polo"
Jonathan Morgan

As already stated, the misfire issues on these can be caused by compression, ignition & injectors. There are also software updates to resolve sticking valve issues, modified fuelling strategies etc....

Tread carefully before taking the head off as there may be an underlying fuelling / software issue which caused the low compression fault in the first instance.

Fixed #

Posted by Paul Goswell on June 6, 2013, 10:17 pm, in reply to "VW Polo 1.4 BUD 2008 - Misfire to #3 cylinder, code P0203 #"
Edited by board administrator June 10, 2013, 1:26 pm

removed head and fluid checked valves no apparrent leaks, but when i removed no 3 cylinder valves the seats on the 2 exhaust vales were very poor and pitted and a lot of carbon build up compared to the other cylinders,so recut allseats and relapped all valves andcar started up fine

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